Exactly how does a coral make its skeleton, a sea urchin grow a spine, or an abalone form the mother-of-pearl in its shell? A new study revealed that this process of biomineralization, which sea creatures use to lock carbon away in their bodies, is more complex and diverse than previously thought.
Researchers studied samples from corals, sea urchins, and mollusks, at edges where mineral precursors—temporary building blocks—start to form the new shell or skeleton. There, they found a surprise: corals and mollusks produced a mineral precursor that had never been observed before in living organisms or rocks, and had only recently been created synthetically.
The surprise mineral precursor, calcium carbonate hemihydrate (CCHH), and another building block (monohydrocalcite, or MHC) were both found in corals and mollusks. But CCHH and MHC only showed up in trace amounts in sea urchin spines—suggesting that different animals take different approaches to biomineralization.
“One fascinating observation is that coral skeletons and mollusk mother-of-pearl form with exactly the same precursors, yet they evolved completely separately from one another,” said Pupa Gilbert, a visiting faculty scientist at Berkeley Lab and professor at the University of Wisconsin, Madison. “That’s cool because it means making a biomineral that way, with so many precursors, is an evolutionary advantage—energetically, kinetically, or some other way,” Gilbert said.
The researchers used two techniques in this work: photoemission electron microscopy (PEEM) at Advanced Light Source (ALS) Beamline 11.0.1.1, and synchrotron infrared nanospectroscopy (SINS) at ALS Beamlines 2.4 and 5.4. A new method, called “myriad mapping,” made it possible to visualize all the different types and relative concentrations of minerals in one image; previous methods were limited to only three. Data processing was done using “massively parallel” natural intelligence, where a diverse group of undergraduates parallel-processed data that had been acquired over eight years.
Gilbert and her collaborators have ongoing research looking at how the increasing acidity of ocean water affects the way sea creatures make biominerals. Understanding the process is key to predicting how marine life will respond to environmental changes such as more acidic oceans caused by climate change.
C.A. Schmidt, E. Tambutté, A.A. Venn, Z. Zou, C. Castillo Alvarez, L.S. Devriendt, H.A. Bechtel, C.A. Stifler, S. Anglemyer, C.P. Breit, C.L. Foust, A. Hopanchuk, C.N. Klaus, I.J. Kohler, I.M. LeCloux, J. Mezera, M.R. Patton, A. Purisch, V. Quach, J.S. Sengkhammee, T. Sristy, S. Vattem, E.J. Walch, M. Albéric, Y. Politi, P. Fratzl, S. Tambutté, and P.U.P.A. Gilbert, “Myriad Mapping of nanoscale minerals reveals calcium carbonate hemihydrate in forming nacre and coral biominerals,” Nat. Commun. 15, 1812 (2024), doi:10.1038/s41467-024-46117-x.
Adapted from the Berkeley Lab news release, “Shedding Light on Sea Creatures’ Secrets.”